OK, so I decided to get a Pistol Wear holster. I got the "Trump Card" model which is a one-pocket Smart Carry-type clone. They also make 1 and 2 pocket models. I only needed a small unit because I already have a Smart Carry.
First impressions: Fabric is more porous so should be cool. Downside is less rugged than Smart Carry, IMO.
Fastens with 3 snaps after adjusting the size with Velcro. This is an improvement, IMO, that you can set and forget. Just fit it and next time you just put it on and it'll fit. Not a big deal, but a little easier, IMO. The whole unit works like Velcro so it is infinitely adjustable. +1 for Pistol Wear.
This model comes with an over-the-shoulder support strap (like a friggin' brassiere! ) so you can wear it in chest carry fashion. I'm still deciding on this. Might be a good option but you'd really need a shirt with buttons or snaps (like my 5.11 Tactical shirt with front snaps instead of buttons that I just got...) and a T Shirt would probably suck for this use.
All-in-all, this looks interesting. I'll assume the other 2 larger models will be about the same except for size. Smart carry or Pistol wear, a self-supported holster that should work well for clothes with out belts or other fasteners.